Screening means for vacuum electric tube devices



March 1948. 'J. M. DODDS ET AL SCREENING MEANS FOR VACUUM ELECTRIC TUBE DEVICES Filed Dec. 29, 1943 [Ml/(N70,?)-

J OHN MATHlESoN Downs ATTYS.

w M D U nu D 1 D N 53 H N m 3% Y 3 @aiented Mar. 23, 1948 SCREENING MEANS FOR VACUUM ELECTRIC TUBE DEVICES John Mathieson Dodds, Timperley, and John Heywood Ludlow, Bowdon, England 7 Application December 29, 1943, Serial No. 516,107 In Great Britain May 13, 1938 3 Claims. 1

This invention relates to high power vacuum electric tube transmitter devices or valves of the kind which are operated in conjunction with appropriate circuits on very low wavelengths of the order of 50 metres and less and even below ten metres, and having wavelength changing arrangements involving the selective connection of different inductances.

The invention aims at providing very high efficiency screening between the anode and grid circuits of a high frequency transmitting valve.

According to the present invention the several inductance coils and the wavelength changing switches of the grid circuit of the valve or valves are located in a metal compartment or chamber and the switch blades are connected to the terminal (or terminals) of the control grid (or grids) of the valve (or valves) by conductors located in screening tubes or a single screening tube directly connecting said compartment or chamber and the terminal of the screening grids in the case of a valve in accordance withBritishLetters Patent No. 497,359 or with a relatively small screening chamher or box applied to a valve in accordance with British Letters Patent No. 414,753 which small chamber is of sufiicient size only to shield the appropriate parts of the valve, with requisite clearence in relation to the voltage differences. It will be understood that the several inductance coils may be mounted on a panel or on pillarsin the relatively large grid circuit chamber or compart-' merit wherein also may be located the tuning condenser, if any, for said grid circuit inductance coils.

In applying the present invention to a valve in accordance with prior British Letters Patent No. 497,359 the screening box 30 shown in Figs. 2, 3 and 4 of specification of British Letters Patent No. 497,360 may be replaced by a metal tube or conduit the end of which fits directly against the side of the central metal envelope member 1 IOI and contains the projecting control grid supporting leads 3i to which are attached the feeders which pass, in an extension of said conduit, to the selector switches in the manner hereinbefore indicated.

In carrying out the invention for a valve or a pair of valves of the kind indicated in'Fig. 1 of British Letters Patent No. 497,360 aforesaid, the screening box may be of such minimum size that it contacts with the condenser 20 and/or I9 and covers the terminals I4 and H, a pair of leads or at least the control grid lead being taken through a, lateral aperture in said screening box and through the tubular conductor associated therewith to the blades of the inductance selector switch, which may be housed adjacent the group of inductances in another sub-compartment of the main cubicle.

To enable the present invention to be fully understood it will now be described by way of eitample with reference to the accompanying diagrammatic drawings, in which:

Figure 1 is a sectional elevation illustrating the present invention and that of Ser. Nos. 516,103, and/or 516,105, applied to a valve which is per se in accordance with British Letters Patent No. 414,753 (aforesaid) and Fig.2isatransverse section showing the present invention applied to the push-pull valve structure which is per se in accordance with British Letters Patent No. 497,359 aforesaid.

Referring to Fig. 1 of the accompanying drawings, the valve therein diagrammatically illustrated, in general comprises the anode I sealed to an insulating tube 2 which is connected to a pipe 3 which in turn is connected with an evacuating pump whereby the valve is continuously or intermittently evacuated during operation. At 4 is shown the filament cathode,.at 5 the control grid and at 6 the screening grid. The screening grid 6 is formed with a conductive'cap So so as to make the screening grid electrically continuous. Obviously there may be further gridssuch for instance as -a suppressor grid between the screening grid 6 and the anode I. Sealed to the top of the anode is an insulating tube I upon which is sealed a metal ring 8 which carries the tubular support 9 of the screening grid 6. Sealed to the metal ring 8 is an insulating ring I0 and sealed to the top of the latter is a metal ring II which carries a support I2, in the form of a half tube, for one end of the filament 4. Sealed above the ring I I is a, further insulating ring I3 upon which is sealed a metal ring I4 which carries the other filament support I5, also in the form of a half tube. Above the metal ring I4 is secured an insulating tube I6, the upper end of which is closed by a plate I! which carries a, tubular support I8 for the control grid 5. At I9 and 20 are shown respectively the screening grid bypass condenser and the filament bypass condenser which condensers areannulan. The numeral I ia designates a connection between the filament terminal I4 and th screening box 27a. This direct connection serves to minimize the inductance of the cathode circuit.

At 2| is shown part of the screening box or subcompartment for the grid circuit inductances 2'2, 23 and 24, which have difierent values and are adapted to be selectively connected, in the example, by wavelength change switches 25 to the grids of a pair of push-pull valves, only one of which is illustrated in the figure. This connection is effected by conductors 26 centrally located in the metal tubes 2'l'which connect the compartment or chamber 2| with the relatively small boxl'la for each of the two valves. Each box 21a houses and shields the appropriate terminals of the valve and in particular the grid terminal I1 thereof. The tuning or trimming condenser 28 for the inductances 22, 23 and 24 is shown located in the compartment or chamber 2|, but it will be obvious that such condenser may be duplicated with one in each of the relatively.

trodes is of a very high order since it is continuous both internally and externally of the valve.

It will be understood furthermore tha'tthe invention is not limited to push-pull valves sinceit may be applied to a single valve.

Referring to Fig. 2 of the accompanying drawings, this illustrates theinvention applied to a push-pull v'alve'in accordance with British Letters Patent No. 497,359 (aforesaid). Secured to the central metal member Hll' of the valve is the tubular member 29 which fits around said central member and extendsto anopening 3|] in the control grid circuit screening 'compartment'or chamber,part of which is indicated at 3|, this'chamber containing, as described with reference to Fig. 1, the grid tuning induc'tan'ces (not shown) adapted to "be selectively connected on the one hand by switch blades of which one is indicated at 32, mounted on a shaft 33 and'carrie'd by the righthand endsof the straight baror other conductors 34 which at their left-hand ends are secured to the 'ter'minal membe'rs 35 of the control grids of thevalve. In thearrangement shown-in Fig.2 the tuningor trimming condenser "for the-grid'inductance-coilsmay belocated in the compartment in chamber 3| or it may be provided, for example,

between the leading-in members 35,'as illustrated by 'way'of example in Figs. 2 and 3 of the drawings of specification of British Letters Patent No. 497,360 (aforesaid).

We claim: 7

'1. In a radio transmitter 'for high frequencies, a valve having acontroi'grid and anode, a resonant circuit electrically connected with said controlgrid, a screening electrode separating the control grid andanode, a'conductive support for said screeningelectrode forming an electrically -con-.

tinuous connection therewith, an electrical screening enclosing said resonant circuit, electrical screening enclosing the connection between the control grid and resonant circuit and'for'ming acontinuous electrical connection on the one'side with the screening "electrodesup'p'ort and on the other side with the resonant'circuit screen, the arrangement being such as to formanelectrically continuous screen between the control gr-id circuit and anode circuit both internally and externally of the valve.

2. In a radio transmitter for high frequencies, a valve having a control g'rid and ano'de,:aresonant circuit, an electrical connection between said control gridand said resonant circuit,'a tubular screening electrode closed at the anode end and separating the anode and controlgrids, a tubular support for said screening electrode, an annular terminal member connected to said electrode support, a terminal support for'the control electrode located in the side of the screening electrode terminal remote from the anode, a'screening box surrounding said control grid terminal, a highi'requency electrically continuous connection between the screening box and the screeningelectrode terminals, a. screening box surrounding the resonant circuit and screening surrounding the connection between the control electrode and resonant circuit, said last mentioned screening forming an electrically continuous connection on the one side with the screening box of the control electrode and on the other side with the screeningbox of the resonant circuit, th arrangement being such that continuous electrical screening is formed between the control grid circuit and the anode circuitboth internally and externally of the valve.

3. In aradio transmitter for high frequencies, a valve having a control grid and anode, a resonant circuit, an electrical connection between said control grid and said resonant circuit, a tubular screening electrode closed at the anode end and separating said anode and control grid, a tubular support for said screeningelectrode, an annular terminal member connected to said electrode support, a terminal support'for the'c'ontrol electrode'located on the side of the screening electrode terminal remote from the anode, a screening box surrounding said control grid terminal, an annular condenser surrounding said valve and having one condenser plate forming an electrically continuous connection with the screening box, an electrically continuous connection between a second'plate'o'f said condenser and said screen electrode support whereby'said condenser acts as a high frequency bypassfor the screening electrode and at the same time maintains continuity of the screening, filament-terminal members located between the control grid terminal and the screen grid terminal, a direct electric connection-between one of said'filament terminals and said screening box, a screening box surrounding said resonant circuit and screening surrounding the electrical connection betweenthe control gridand resonant circuit and forming electrically continuous connections on the one side with the control grid screening box and on the other side with the resonant circuit'screening box, the arrangement being such that an-electrica1ly continuous screening'is formed between the control'grid circuit and the anode circuit both internally and externally of the valve.

JOHN M'ATHIESON DODDS. JOHN HEYWOOD -LUDLOW.

REFERENCES CITED "The following references are of record in the "file of this patent:

, -s'rii'rns PATENTS Number France Mar. 15, 1932 

